Poly(trimethylene terephthalate) (also referred to as “PTT”) has received much attention as a polymer for use in textiles, flooring, packaging and other end uses. Textile and flooring fibers have excellent physical, chemical and dyeability properties.
It is well known that highly desirable crimp contraction properties, which lead to increased value in use for fibers, can be achieved by bicomponent fibers where the two components either have differing degrees of orientation, as indicated by differing intrinsic viscosities, or where the two components are different polymer species.
For example, U.S. Pat. No. 3,671,379 and U.S. Pat. No. 6,692,687 B2 disclose bicomponent polyester textile fibers wherein one of the components is poly(trimethylene terephthalate) and the other is poly(ethylene terephthalate).
US 2004-222544 A1 describes the preparation of bicomponent fibers where both components comprise poly(trimethylene terephthalate) with different physical properties. U.S. Pat. No. 6,641,916 B1 teaches the preparation of a side-by-side or eccentric sheath-core bicomponent fiber wherein each component comprises a different poly(trimethylene terephthalate) composition and wherein at least one of the compositions comprises styrene polymer dispersed throughout the poly(trimethylene terephthalate).
JP 11-189925 describes the manufacture of sheath-core fibers comprising poly(trimethylene terephthalate) as the sheath component and a polymer blend comprising 0.1 to 10 weight %, based on the total weight of the fiber, polystyrene-based polymer as the core component. According to this application, the core contains polystyrene and the sheath does not. Example 1 describes preparation of a fiber with a sheath of poly(trimethylene terephthalate) and a core of a blend of polystyrene and poly(trimethylene terephthalate), with a total of 4.5% of polystyrene by weight of the fiber.
JP 2000-256918 A discloses sheath-core or side-by-side bicomponent fibers wherein one side (A) comprises at least 85 mole percent poly(trimethylene terephthalate) and the other side comprises (B) at least 85 mole percent poly(trimethylene terephthalate) copolymerized with 0.05-0.20 mole percent of a trifunctional comonomer; or the other side comprises (C) at least 85 mole percent poly(trimethylene terephthalate) not copolymerized with a trifunctional comonomer wherein the inherent viscosity of (C) is 0.15 to 0.30 less than that of (A). It is disclosed that the bicomponent fibers obtained were pressure dyed at 130° C.
None of the aforementioned references discloses side-by-side or sheath-core bicomponent fibers where both components contain substantial amounts of the same poly(trimethylene terephthalate), nor do they disclose such poly(trimethylene terephthalate) containing bicomponent fibers that also contain a polyether based-component.
It is desired to prepare poly(trimethylene terephthalate) fibers with excellent crimp contraction, dyeability and softness. The invention described herein achieves these goals.